BRPI0622032A2 - METHOD, ARRANGEMENT AND SYSTEM FOR EASY COMMUNICATION IN A TELECOMMUNICATION SYSTEM, AND MANUFACTURING ARTICLE IN A TELECOMMUNICATION SYSTEM USED TO EASY COMMUNICATION - Google Patents

Description

“METHOD, ARRANGEMENT AND SYSTEM FOR EASY COMMUNICATION IN A TELECOMMUNICATION SYSTEM, AND, MANUFACTURING ARTICLE IN A TELECOMMUNICATION SYSTEM USED TO EASY COMMUNICATION” TECHNICAL FIELD

The present invention relates to methods and arrangements in a telecommunications system for facilitating communication between a first terminal configured to use a first media transport session model, and a second terminal configured to use a second transport session model. from media.

INTRODUCTION

IP IMS Multimedia Subsystem is the technology defined by the Third Generation Partnership Project to provide IP multimedia services over mobile communication networks (3GPP TS 22.228, TS 23.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 Release and Release 6). IMS provides core capabilities for enriching the end-user person-to-person communication experience through the use of standard IMS Service Enablers, which facilitate rich new person-to-person (client-to-client) communication services as well as person-to-content services ( client to server) over IP-based networks. IMS makes use of SIP Initiation Protocol to configure and control calls or sessions between user terminals (or user terminal and server applications). The SDP Session Description Protocol, carried by SIP signaling, is used to describe and negotiate session media components. While SIP was created as a user-to-user protocol, IMS allows operators and service providers to control user access to services and consequently charge users.

IP multimedia services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. As the number of basic applications and media that can be combined increases, the number of services offered to end users will grow, and the experience of interpersonal communication will be enriched. This will lead to a new generation of rich and personalized multimedia communication services, including so-called “IP Multimedia Combined” services.

The concept behind blended services involves bundling the voice service into an existing CS circuit switching domain with the "content" in the PS packet switching domain. It uses standards-based voice and data networks that are, to a large extent, already in use by operators. An example of combined services is when a voice call is set up as normal in the CS domain and then while the call is in progress, content such as images, videos and files can be added or removed through the PS domain. This enriches voice communication and enhances interaction between voice and data services creating a number of new business opportunities for mobile operators. The end-to-end combined services solution is highly scalable, robust and in line with 3GPP Combination CS specifications and IMS CSI services and is based on the IMS architecture as specified by 3GPP.

Fixed IMS deployments support a variety of services such as IMS MMtel Multimedia Phone, file transfer and Instant Messaging, etc. 25 IMS Multimedia Phone offers new and attractive services to the residential market. Operators can expand their current PSTN Public Switched Telephone Network by offering one or several IP telephone lines for each home. IMS Multimedia Phone is based on the IMS standard specified by 3GPP. Further the solution is built according to a standardization conducted by TISPAN that monitors additional requirements from the fixed network perspective. IMS Multimedia Phone reduces costs by allowing direct addition of new applications and service evolution from Telephony over IP to Video telephony for convergence of mobile / fixed communication. In IMS Multimedia Phone, a single session template is used for multiple media transport, e.g. g. Voice and video are negotiated and configured as a signaling session. Figure 1 is part of the prior art and schematically discloses communication between Al and A2 multimedia telephony terminals both using media transfer according to a "ONE" session model. The additional node entities shown in Figure 1 will be explained later in the description when the invention is discussed.

Currently CSI (Combination CS and IMS Services) is a 3 GPP defined service used to enrich the experience of a mobile communication CS circuit-switched communication session such as voice with a simultaneous IMS session. The IMS session could be a video stream, image transfer or other types of media transfer.

While in MMMS IMS Multimedia Phone, voice and video are negotiated and configured as a signaling session, in the case of CSI, voice is configured with a CS session and e.g. video is configured with a parallel IMS session i. and. MMtel uses a one session model and CSI uses a two session model. Communication between terminals using different session models poses a malfunction.

US Patent Application 2006/0126590 discloses method for receiving data in a system where data is transmitted on a large amount of frequencies. A device determines a setting associated with a selected session and receives the session according to a particular setting. In a CSI scenario for MMtel the mismatch affects a one-way session relative to a two-way session where the second session could result in a busy MMtel client response.

5 An additional problem is the need to reroute

of the session. US Patent Application 2004/0160895 A1 discloses a failure notification followed by appropriate rerouting.

A voice session initiation from MMtel to CSI will result in routing in the Packet Switching domain followed by a rejection of CSI, since CSI does not support Voice over Packet Switching, only Voice over Circuit Switching. MMtel uses the IMS domain to configure according to the one session model while CSI uses both the IMS and CS domains to configure according to the two session model. Caller preferences for the 15 Session Initiation Protocol can be found in standards documents such as RFC 3841.

SUMMARY

The present invention solves a problem related to communication between terminals using different session models. For a one-session model terminal to be able to communicate with a two-session model terminal, a session must be divided into two sessions or two sessions must be joined into one. For example, in a CSI to MMtel scenario, if this is not done, the second session could result in an error or busy response from the MMtel client. However, splitting or joining sessions entails obstacles due to inherent differences in session types. An additional problem is the inability of an IMS Core Network to interrupt Circuit Switching for a session intended for a registered user. Interruption only occurs if the called subscriber is not registered within the system. In this case the subscriber is registered in the system but due to inability to communicate between a one session model terminal (such as MMtel) and a two session model terminal (such as CSI), no indication will be found in the Domain Control domain. IMS during session setup showing the need for routing in the Circuit Switching domain for both terminals to be able to communicate.

According to the invention, communication problems are solved by making it easier for the terminal of a session to circumstantly select to communicate either according to a one session model or according to a two session model. Deducting registration data related to a target user allows the source user to select which type of template to use, i. and. depending on what type of template the target user supports.

The solution to the most detailed problems comprises a method for facilitating communication in a telecommunication system between a first terminal configured to use a first session model and a second terminal configured to use a second session model for media transport. The method comprises the following steps:

- A serviceability check is initiated from the first terminal.

- Capacity resources related to the second terminal are received for the first terminal.

Establishing the fact that the second terminal is configured to use the second session model.

- The first terminal is reconfigured for use by the second session model.

According to a further aspect of the invention, the additional problem is solved by making a representative register in the control domain in the telecommunications system. The representative register allows routing in the circuit switching domain.

An object of the invention is to improve the ability for IMS / SIP clients such as an MMtel client to make enhanced voice calls to combined IMS / CS clients such as a CSI terminal. This object and others are achieved through methods, arrangements, systems and articles of manufacture.

An advantage of the invention is that it realizes a way to support interworking between IMS / SIP session endpoints and fixed CSI two-session terminals.

Another advantage with the invention is that it introduces a representative logging function to allow the use of IMS functionality in the context of CSI interworking.

The invention will now be described in more detail with the aid of preferred embodiments in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is part of the prior art and discloses a block schematic illustration of the IP Multimedia subsystem in conjunction with access networks and main network when media is transferred according to a one-session model.

Figure 2 discloses a block schematic illustration of the IP Multimedia subsystem in conjunction with the access and main network networks when media is transferred between a reconfigured MMtel terminal and a CSI terminal according to a two session model. Voice and video are started from the MMtel terminal.

Figure 3 discloses a signal sequence diagram for voice call configuration from MMtel to CSI followed by video initiation from MMtel.

Figure 4 discloses a block schematic illustration of the IP Multimedia subsystem in conjunction with access networks and main network when media is transferred between a reconfigured MMtel terminal and a CSI terminal according to a two session model. Voice and video are started from the CSI terminal.

Figure 5 discloses a signal sequence diagram for

Voice call setup from CSI to MMtel followed by video initiation from CSI.

Figure 6 discloses a flow chart illustrating some essential steps of the method of the invention.

Figure 7 schematically discloses an arrangement that can be

be used to put the invention into practice.

DETAILED DESCRIPTION

Figure 2 discloses a telecommunications system comprising an IMS-A and IMS-B IP Multimedia Subsystem that monitors signaling in a control domain. Media such as voice and video is mostly monitored in a bearer domain. The carrier domain in the example consists of an ACC NW access network (such as PLMN and PSTN) and a UMTS UTRAN Terrestrial Radio Access Network and an IP NW master network. An MMtel client A is located on the ACC NW access network while a CSI client B is located on the UTRAN access network. MMtel Client A is a one-session client used for multiple media. Voice and video for example are negotiated and configured as a signaling session. According to the invention, the MMtel device is reconfigurable to select to communicate according to a one session model or according to a two session model. This reconfiguration of the MMtel device will be further explained later in the description. The CSI Client is a two-session client that communicates signaling and media to / from the IMS IP Multimedia Subsystem through a radio base station and an RNC Radio Network Controller. Signaling / media here passes through an MSC Mobile Service Switching Center in the CS Circuit Switching domain or a GGSN Connection Point GPRS Support Node in the PS Packet Switching domain. The control domain in the example comprises two IMS networks, one source network in this example, IMS-A, and one IMS-B destination network. In Figure 2 each IMS network comprises a CSCF-A and CSCF-B Session / Call Control Function. CSCFs are SIP servers and essential nodes in IMS. A CSCF processes SIP signaling on the IMS network. The CSCF comprises different types of Call / Session Control Functions such as P- / I- / S-CSCF as defined in the standards, but are for the sake of clarity shown in the schematic of Figure 2 as a single node. P-CSCF acts among others as the first point of contact (in the signaling plane) between a terminal and the IMS network, the S-CSCF is a central node of the signaling plan and controls the session. An MGC Media Connection Point Controller receives CSCF-B SIP signaling and transforms SIP signaling into ISDN User Part ISUP signaling. ISUP is used in the field of Circuit Switching in the configuration, management, and release of trunks that carry voice and data between called and calling parties. An RS Registration Condense Information node registers a contact with CSCF-B. This contact contains information necessary for CSCF-B to route a request correctly. RS is a SIP User Agent Client that makes a representative registration on behalf of a device such as a Circuit Switching device that may not explicitly register with the CSCF-B.

A first embodiment of the invention will now be introduced with FIG. 3. The method disclosed in FIG. 3 comprises A to B voice call setup followed by A initiating video setup. The method will show a record control that clarifies to source client A which session model destination client B uses i. and. a two-session model in this example. The method will also show signaling routing in the CS domain and also setup a parallel voice / video in two session communication. A prerequisite for the invention is that client A of a session is prepared to reconfigure itself to use the two-session model as well and has explicitly recorded contact for both CSI and MMtel in CSCF-A. Figure 3 is divided into four signaling groups, i. and. REGISTRATION, CALL, SERVICE VERIFICATION AND VIDEO. The entities we such

like CSCF, RS, etc. already explained in figure 2. The method according to the first embodiment of the invention comprises the following steps:

- A contact Tag = CSI & MMtel, a so-called first resource label, is stored in CSCF-A as part of the registration data.

to customer A. The contact is sent AI from A to CSCF-A. The contact contains the information necessary for CSCF-A to route any MMtel or CSI request to customer A.

- Client B, i. and. CSI client, connects to the CS Circuit Switching network and an IB signal is sent through the MSC from

from B to the Condense Information Registration node RS.

- RS registers client A, i. and. the MMtel client that is configurable to communicate using either the one or two session model. The register is shown in the figure with a 1C signal. A contact Tag = MMtel, a so-called second resource label, is here.

stored in CSCF-B as part of the registration data for client B. Registration can occur either dynamically, as in the step above, or statistically, i. and. by disposition. If dynamic registration is desired, it could be implemented using CAMEL triggers or

OSA / Parlay / Parlay Services X Status. Through static registration, the registration is manually configured in RS. The RS then e. g. periodically updates the CSCF-B. The contact contains information necessary for CSCF-B to route any MMtel request to device B through MGC and MSC in the Circuit Switching domain.

CALL

- Client A initiates an MMtel voice session from source client A toward destination client B via CSCF-B by sending a SIP INVITATION request 2A. CSCF-B finds contact from MMtel, i. and. Tag = MMtel, for the CSI mobile communication device and therefore forwards the SIP signaling request 2A to the MGC. MGC is a state machine that does protocol translation and in this example MGC maps SIP to ISUP. MGC directs ISUP signaling request 2B through the MSC in the Circuit Switching domain to client B.

- Client B responds with an acknowledgment by sending a 2C acknowledgment signal through the MSC to the MGC. After 2C conversion, a 2D SIP 200 (OK) response signal is sent from the MGC to client A according to Figure 3.

- A voice session is now established between clients. The session consists of Real Time Protocol RTP VOICE 22A between Client A and MGW Media Connection Point, PCM Pulse Code Modulation VOICE 22B between MGW and MSC, and AMR Adaptive Multitax VOICE 22C between MSC and Client B.

SERVICE VERIFICATION

- A capability check is performed using a SIP OPTIONS signal 3 A sent from client A via GGSN Connection Point GPRS Support Node in the PS Packet Switching domain for client B.

- Client B responds by sending a SIP OPTIONS signal 3B to client A according to Figure 3. The SIP OPTIONS signal comprises a "CSI" record showing that client B supports CSI. In this case remote client B only supports CSI, so source client A knows how to use the two session model for any additional media.

- Device A is reconfigured and is now ready for use with the second TWO session template. Reconfiguration is marked with X in Figure 2. A prerequisite for reconfiguration is that the device be prepared to respond to the above SIP OPTIONS signal through reconfiguration.

- Same kind of signage as above is sent in opposite directions. During this signal, client B asks client A what signal client A supports and A responds (this signal is not shown in figure 3)

VIDEO

- Client A initiates a CSI Video session towards client B by sending a SIP INVITATION request 4A according to Figure 3. Client B responds by sending a SIP 200 (OK) signal 4B to A.

- A two way video session is now established between clients. The session consists of VIDEO 44 Real Time Protocol between AeB clients.

Video session session initiation could likewise come from client B. Note also that Figure 3 only shows the general principles of signaling. Of course, signaling will vary depending on existing circumstances such as whether IMS-A or IMS-B are acting as home or visited networks for AeB subscribers respectively. Further, the signaling protocol type is only briefly mentioned but can be found in standard related documents. Also to be noted is that the labels (CSI and MMtel) mentioned above are to be seen as examples. Any resource label could be used.

Figure 4 generally corresponds to that already explained in figure 2.

However, in

Figure 4 IMS-B is the source network for IMS and IMS-A is the source network.

of destination. An MGW Media Connection Point and an MGC Media Connection Point Controller used in the invention are in the second mode located on IMS-A instead of IMS-B as in the first mode.

Figure 5 discloses a second embodiment of the invention. The method disclosed in FIG. 5 comprises the voice call setup from B to A followed by B initiating video setup. In this case IMS-B is the source network of IMS while IMS-A is the destination network. The method as in the first mode will show the configuration of a voice / video in parallel in two session communication. The method according to the second embodiment of the invention comprises the following steps:

RECORD

- Registration is performed in the same manner as in the first mode i. and. A contact Tag = CSI & MMtel is stored in CSCF-A.

CALL

- Client B initiates a CSI voice session from the

source client B toward destination client A through MGC located on destination network IMS-A to CSCF-A by sending a SETUP signal 5A. MGC transforms ISUP signaling into SIP signaling. CSCF-A finds CSI contact, i. and. Tag = CSLfcMMtel and 25 therefore directs a MGC SEP signaling request 5B to client A.

Client A responds with an acknowledgment by sending an acknowledgment signal 5C i.e. a response signal from SIP 200 (OK) via the MGC. After 5C conversion, an ISUP 5D acknowledgment signal is sent from the MGC to the MSC on the source network according to figure 5. - A voice session is now established between clients.

The session consists of VOICE 55A Real Time Protocol RTP between Aeo Client and MGW Media Connection Point, VOICE 55B PCM Pulse Code Modulation between MGW and MSC, and AMICE Adaptive Multitax VOICE 55C between MSC and client B.

SERVICE VERIFICATION

- A service check is performed using a SIP OPTIONS signal 6A sent from client B through GGSN Connection Point GPRS Support Node in the PS Packet Switching domain to client A.

- Client A responds by sending a SIP OPTIONS signal 6B by sending the SIP to client B. The SIP OPTIONS signal comprises a "MMtel" record (not shown in the figures) showing that client A supports MMtel.

- A capacity check is performed using a SIP OPTIONS 6C signal sent from client A via the

GGSN Connection Point GPRS Support Node in the PS Packet Switching domain for client B.

- Client B responds by sending a SIP OPTIONS signal 6D to client A. The SIP OPTIONS signal comprises a "CSI" record (see Figure 4) showing that client B supports CSI. In this case remote client B only supports CSI, so source client A knows how to use the two-session model for any additional media.

- Device A is reconfigured and is now ready for use with the second TWO session template. The reconfiguration is marked with X in figure 2.

VIDEO

- Client B initiates a CSI video session toward client A by sending a SEP INVITATION request 7A. - A two way video session is now established for clients. The session consists of VIDEO 77 Real Time Protocol RTP between AeB clients.

Video session initiation could similarly come from client A. This has already been shown in the first embodiment.

Figure 6 discloses a flowchart in which some important steps are shown. The flowchart is to be read along with the figures shown above. The flowchart comprises the following steps:

A serviceability check is initiated and sent from the first terminal A to the second terminal B. This step is shown in figure 6 with a block 101.

- ”CSI” capability resources related to second terminal B are received for A. First terminal A states that B is configured to use a second session model. This step is shown in figure 6 with a block 102.

- The first terminal A is reconfigured to use the same session model as B i. and. the second session template. This step is shown in figure 6 with a block 103.

An arrangement that can be used to practice the invention is shown schematically in Figure 7. Figure 7 discloses the IMS network and user devices A and B. User device A corresponds to client A described above and User device B corresponds to client B described earlier. User device A comprises a PR1 processor unit that receives, monitors, and sends signals such as register and media configuration signals to EMS and B. PR1 includes the ability to receive and respond to an option signal and reconfigure a receiving device. / send AR / S to receive / send media according to one session template or two session template. A PR2 processor unit in the IMS network monitors registry and media configuration. A REG registration unit on the IMS network receives registration data from A, B, or an RS Registration Condense Information device through the PR2 processor unit. Registration data is stored in the REG. An R routing device is responsible for routing through the CS Circuit Switching domain. B operates in the PS Packet Switching and CS Circuit Switching domain. B receives / sends media in the PS domain through a Bl-R / S Receiver / Transmitter and receives / sends media in the CS domain through a B2-R / S Receiver / Transmitter.

In the figures enumerated items are shown as individual elements. In effective embodiments of the invention, however, they may be inseparable components of other electronic devices such as a digital computer. Accordingly, the actions described above may be implemented in software that may be incorporated into an article of manufacture that includes a program storage medium. Program storage means includes data signal embedded in one or more of a carrier wave, a computer disk (magnetic, or optical (eg, CD or DVD, or both), nonvolatile memory, tape, system memory, and a computer hard drive.

The invention is not limited to the examples shown above. Various kinds of network types may be used by the invention such as PSTN, PLMN etc. The configuration of the IMS can, as already indicated, several species. Noteworthy is also the fact that the labels (CSI and MMtel) mentioned in this document are to be seen as examples.

r

Any resource label could be used. Of course, the invention is not limited to that described above and the embodiments shown in the drawings but may be modified within the scope of the appended claims.

Claims (23)

Method for facilitating communication in a telecommunications system between a first terminal (A) configured to use a first session model (ONE), and which days media sections are negotiated and configured as a signaling session, and a second terminal (B) configured to use a second session model (TWO), and two media sessions are configured in parallel as two signaling sections for media transport, characterized in that it comprises the following steps: service capacity of the first terminal (A); - receiving to the first terminal (A) capacity resources of (“CSI”) related to the second terminal (B); - Establishing that the second terminal (B) supports only the second session model (TWO) by which the first terminal (A) selects to communicate according to the second session model (TWO). Method according to claim 1, characterized in that it comprises the following additional step: - registering a first resource label (CSI & MMtel) in a control domain in the system, representing a contact between the first terminal (A) and the second one. terminal (B). Method according to claim 1 or 2, characterized in that it comprises the following additional steps: - registering a resource label (MMtel) in a control domain in the system, representing a contact between the first terminal (A) and the second terminal (B); -start (INVITATION-1) setup of a first media session (voice) between terminals (A, B); - detection of the first registered label (MMtel); - Routing the first media session through a circuit switching domain (CS). Method according to claim 3, characterized in that the second label (MMtel) is registered either statistically or dynamically through a Condensed Information Register (RS). Method according to claim 4, characterized in that the second label (MMtel) is statistically recorded by manually entering the Condensed Information Register (RS). Method according to claim 4, characterized in that the second label is dynamically registered through the label (MMtel) entry to the Condensed Information Register (RS) when the second terminal (B) enters the system. Method according to claim 6, characterized in that the second label is dynamically registered by the implementation of CAMEL or OSA / Parlay / Parlay X State Services triggers. Method according to any one of claims 2 to 7, characterized in that it comprises the following additional step: - initiating (INVITE-2) configuration of a second media (video) session in the packet switching (PS) domain between terminals (A, B), parallel to the first session (voice). Method according to any of claims 2 to 8, characterized in that the first label (MMtel & CSI) is registered in a Session / Call Control Function (CSCF-A) in which user data (A) of first terminal are stored. Method according to any one of claims 3 to 8, characterized in that the second label (MMtel) is registered in a Session / Call Control Function (CSCF-B) in which the user data (B) of the second terminal are stored. Method according to any of the preceding claims, characterized in that the first terminal (A) is arranged to communicate using the first session model (ONE) or the second session model (TWO). Arrangement for facilitating communication in a telecommunications system between a first terminal (A) configured to use a first session model (ONE), and that the two media sessions are negotiated and configured as a signaling session, and a second terminal (B) configured to use a second session model (TWO), and that the two media sessions are configured in parallel as two signaling sections for media transport, characterized by the fact that it understands. means for initiating at the first terminal (A) a service capability check; means for receiving to the first terminal (A) capacity resources ("CSI") related to the second terminal (B); means at the first terminal (A) for establishing that the second terminal (B) supports only the second session model (TWO); means at the first terminal (A) for selecting communication according to the second session model (TWO). Arrangement according to claim 12, further comprising means for registering a first resource label (CSI & MMtel) in a control domain in the system, representing a contact between the first terminal (A) and the second terminal ( B). Arrangement according to claim 12 or 13, further comprising: - means for registering a second resource label (MMtel) in a control domain in the system, representing a contact between the first terminal (A) and the second terminal (B); means for initiating (INVITATION-1) configuration of a first media session (voice) between terminals (A, B); - means for detecting the first registered label (MMtel); means for routing the first media session through a circuit switching domain (CS). Arrangement according to claim 14, characterized in that the second label (MMtel) is registered either statistically or dynamically through a Condensed Information Register (RS). Arrangement according to Claim 15, characterized in that the second label (MMtel) is statistically recorded through a manual entry for the Condensed Information Register (RS). Arrangement according to claim 15, characterized in that the second label is dynamically registered through the label (MMtel) entry to the Condensed Information Register (RS) when the second terminal (B) enters the system. Arrangement according to claim 17, characterized in that the second label is dynamically registered by the implementation of CAMEL or OSA / Parlay / Parlay x State Services triggers. Arrangement according to any one of claims 14 to 18, further comprising means for initiating (INVITE-2) configuration of a second media (video) session in the packet switching domain (PS) between terminals (A , B), in parallel to the first session (voice). Arrangement according to any of claims 13 to 19, further comprising means for registering the first label (MMtel & CSI) in a Session / Call Control Function (CSCF-A) in which user data (A) of the first terminal are stored. Arrangement according to any one of claims 14 to 20, characterized in that it further comprises means for registering the second label (MMtel) in a Session / Call Control Function (CSCF-B) in which the user data (B) of the second terminal are stored. 22. A system for facilitating communication in a telecommunications system between a first terminal (A) configured to use a first session model (ONE), and the two media sessions are negotiated and configured as a signaling session, and a second terminal (B) configured to use a second session model (TWO), and two media sessions are configured in parallel as two signaling sessions for media transport, characterized in that it comprises: -means to register (Tag = MMtel Tag = CSI) in a control domain in the system, possibilities for mutual communication between the first terminal (A) and the second terminal (B); means for initiating (INVITATION-1) configuration of a first media session (voice) between terminals (A, B); means for routing the first media session through a circuit switching domain (CS); means at the first terminal (A) for establishing that the second terminal (B) supports only the second session model (TWO); means at the first terminal (A) for selecting for communication according to the second session model (TWO). 23. An article of manufacture in a telecommunications system used for facilitating communication between a first terminal (A) configured to use a first session model (ONE), and two media sessions are negotiated and configured as a signaling session, and a second terminal (B) configured to use a second session model (TWO), wherein two media sessions are configured in parallel as two signaling sessions for media transport, characterized in that it comprises: - readable program code a computer capable of initiating a service capability check from the first terminal (A); computer readable program code capable of receiving to the first terminal (A) capacity resources ("CSI") related to the second terminal (B); - computer readable program code capable of establishing that the second terminal (B) is configured to use the second session model (TWO); - computer readable program code at first terminal (A) capable of selecting for first terminal (A) for communication according to second session model (TWO).